Just another piece to your puzzle.
In the danish police records you find that Carl Sophus Charles Sundby was a sailor (styrmand).
1 nov 1902 he moved from Grenaa to Copenhagen to the adress Blegdamsvej 130.
1 may 1903 he moved to Trepkasgade 4 still in Copenhagen
1 may 1903 he moved to Nannasgade 4 still in Copenhagen
1 nov 1910 he moved to Aarhusgade 56 still in Copenhagen
1 nov 1912 he moved from Copenhagen.